Messages in this thread | | | Date | Wed, 21 May 2014 07:36:34 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH] block: mq flush: fix race between IPI handler and mq flush worker |
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On Wed, May 21, 2014 at 01:16:14PM +0800, Ming Lei wrote: > I am wondering if virtio-blk is trivial block driver, :-)
It's about as simple as it gets.
> > The scsi-mq work that I plant to submit for the next merge window is > > the prime example. > > It depends if one scsi-mq req has to requeue itself with rq->requeue_work > inside its own .softirq_done_fn. If yes, we can't put call_single_data > and requeue_work into one union simply. From you last scsi-mq post, > looks the request may do that if I understand correctly.
Requeueing a request from the completion handler is indeed what we'll need with various more complete drivers.
> I think the patch is clean and simple, with documenting the special > conflict case clearly too.
While I can't say anything against the fact that it fixes the issue it's neither clean nor simple.
> Follows current ideas: > 1), this patch with scsi-mq sharing abort_work together? > 2), move requeue_work out of the union inside request > 3), spin_lock_irqsave(&ctx->lock) everywhere and requeue > request directly to ctx without using work
I think Jens very much wanted to avoid irq disabling in the I/O path if possible. If we have a separate requeue list with it's separate lock we can avoid that unless we actually have to take requests of that requeue list. I can look into that implementation.
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